1. Field of the Invention
The present invention relates, in general, to a process for generating chlorine dioxide and, more particularly, to a process for generating chlorine dioxide from pure water and hypochlorous acid. Also, the present invention is concerned with an apparatus utilized in the generation.
2. Description of the Prior Art
Chlorine dioxide (ClO.sub.2), a reddish brown gas, has a specific gravity of 3.0 g/l, a melting point of -59.degree. C., and a boiling point of 11.degree. C. It has a tendency to explode and decompose around 100.degree. C. In addition, it is well dissolved in water and reacted with warm water to decompose into chlorine (Cl.sub.2) and hypochlorite (HClO). A careful treatment can delay such decomposition of chlorine dioxide, which enables it to be used for various purposes.
Strong oxidation and sterilization ability of chlorine dioxide allows it to be used for treating a variety of water, such as tap water, underground water, mineral water, water in swimming pool, waste water, bleaching or decoloring water, water for washing fruits, vegetables and fishes, water for ice manufacture, industrial water, chilling water, hospital water and etc. In addition, chlorine dioxide is useful to maintain freshness of foodstuffs, such as fresh, fishes, vegetables and fruits. Furthermore, it is utilized as a sterilizing and deodorizing agent for refrigerator, food container, automobile, toilet and the like.
There have been developed many methods for producing chlorine dioxide directly at spots. Most of them are now being advanced to automatic operating systems where a process of incorporating proportional precursors for chlorine dioxide is provided for the generation part of a chlorine dioxide generator and an enough reaction time is set.
Much are known about the generation of chlorine dioxide. For example, representative are a method of reducing sodium hypochlorite (NaClO) or sodium chlorate (NaClO.sub.3) to sulfur dioxide (SO.sub.2) in the presence of sulfuric acid and culinary salt and a method of reacting calcium chlorate (Ca(ClO.sub.3).sub.2) with hydrochloric acid. However, these methods produce chlorides such as sodium chloride (NaCl), by-products. In order to avoid production of the chlorides, there is studied another generation method of chlorine dioxide, which comprises reaction of sodium chlorite with hydrochloric acid. This method, however, requires an excess of hydrochloric acid for increasing the reaction rate, which demands a washing step. Use of hydrochloric acid or chlorine gas as material compels careful care to be taken.